beam making question.

[SilverBox]

I have a 20' long 20" or so diameter section of doug fir that I want to make a 6" x 14" x 17' beam out of. However it has a bow in about 6 feet up from the base. The bow is maybe 12-15" of deflection, I think I can mill the piece I want out of the log, but it will have to angle across the grain at one end of the beam, if that makes sense.

Do you think that will significantly weaken the beam? I need about 1200 Fb and I'm not sure that the beam will have it check this grading chart:

Douglas Fir-Larch
Beams and Stringers
Dense Select Structural 1850 PSI
Select Structural 1600 PSI
Dense No.1 1550 PSI
No.1 1350 PSI
Dense No.2 1000 PSI
No.2 875 PSI

Edit: I found this book, I'm reading it now, what I'm talking about they define as diagonal grain. http://books.google.com/books?id=2g...=X&oi=book_result&resnum=4&ct=result#PPA24,M1

Edit2: I think it will be ok, the defining factor appears to be grain slope, so long as its 1:12 or better on the end 1/3 where the bow is it should be strong enuf, I don't think it will exceed that.

 

[Brmorgan]

If it's diagonal on the narrow face (slopes from back to front) and the piece is used on edge, it shouldn't affect the strength a great deal, as the force on the beam will still be perpendicular to the grain deviation. I'm a lumber graderman by trade and slope of grain (diagonal grain) can greatly affect lumber's strength, so it isn't to be taken lightly. Is the beam going to be used in a situation requiring inspection? However the bigger problem I think you're going to have is keeping a beam cut like that straight as it dries.

PS - if you want any info out of the newest NLGA grading rule book let me know and I can scan or type it out for you.

 

[SilverBox]

Yeah I was planning on milling it so that the diaganol would be on the narrow face, seemed stronger that way as the load is being applied to the top. It doesn't matter if it bows a lil bit drying, I'm planning on using it fairly soon after milling and nailing all the joists to the top of it should keep it from moving to much, the joists will also overlap on top of it. It will not be need to be graded its for an ag building (barn).

This is all probably overkill, because I doubt I'll ever even come close to the load on it that I'm designing for, but why build it weak .

So how expensive is it to get lumber graded? Does it vary from state to state? I've toyed with the idea of making lumber for residential construction, but I've never checked into how you get it graded.

 

[deeker]

If it's diagonal on the narrow face (slopes from back to front) and the piece is used on edge, it shouldn't affect the strength a great deal, as the force on the beam will still be perpendicular to the grain deviation. I'm a lumber graderman by trade and slope of grain (diagonal grain) can greatly affect lumber's strength, so it isn't to be taken lightly. Is the beam going to be used in a situation requiring inspection? However the bigger problem I think you're going to have is keeping a beam cut like that straight as it dries.

PS - if you want any info out of the newest NLGA grading rule book let me know and I can scan or type it out for you.

Great post with lots of information, I am a small mill owner and interested in all I can learn. Always willing to learn.

Sent you a PM.

Kevin

 

[Brmorgan]

So how expensive is it to get lumber graded? Does it vary from state to state? I've toyed with the idea of making lumber for residential construction, but I've never checked into how you get it graded.

I have no idea either. As I just told Deeker in a PM, up here in Canada anyway the mills basically "lease" their stamps from the local Lumber Associations (ours is the Council Of Forest Industries, aka COFI, in the BC interior) for an annual fee. Because of this the mills are subject to frequent inspections from the association to make sure they're grading up to standards, and if they're not the association can pull the mill's stamp and not allow them to produce any more until the problem is fixed. Also I should note that each mill has its own unique number on its stamp, so it cannot be used elsewhere. So I have no idea if it's even possible for private individuals to acquire a stamp, and it might be prohibitively expensive if it were possible. If I get a bandmill this year (looks like it might happen) I will likely be looking into it though.

 

[Backwoods]

Out here the guy that travels around to inspect the big mills (West Coast Lumber Inspection Bureau) will stop in once a month if I give him a call and grade any lumber that I need graded on an hourly rate $62.50 with a one hour min. The most he ever charged me was for three hours, two hours of grading and an hour for the paper work end of it. Seemed to be a good deal as I had a whole house package laid out for him so he could get right to work, and I stayed out of his hair.

 

[SilverBox]

Well I got a rain free day to try milling up that bent log. Took a few pics, I guess it turned out ok, but I still have to mill the sides. Also, its about 2.5 feet longer then it needs to be right now, but the big end has a curve to it, so I'll take the 2.5 I don't need off of it.

 

[peterrum]

So far so good. Looking forward to seeing the end of it.

 

[excess650]

did you use a Granberg Mini Mill or something else?

 

[SilverBox]

did you use a Granberg Mini Mill or something else?

yeah granberg mini mill, and the longest bar I have is 20" and it didn't reach all the way thru, so I had to mill it about 16" deep and then pull the board off and take the saw out of the mill and freecut the last few inches of the cut, pain in the butt, I need a bigger bar

I'm gonna get a bigger bar and weld up an alaskan in the next few weeks.

 

[BobL]

I'm not sure how how much milling you have done but you seem to be getting a lot of 'steps' in the cut for what is a very softwood.

I understand you freehand cut one side but the steps are on both sides so at least one side it should be reasonably stepless.

This happens when the saw is twisting because it is either being pushed too hard because the chain is not sharp, or the mill is not fitting properly on the top board. This is a limitation of the mini mill so an alaskan will improve this to some extent but it can still happen using an alaskan especially towards the end of the cut in hardwood where the chain is getting blunt.

When cutting narrow boards, any steps can be taken out with a thicknesser but it may not be as easy to do this will a beam.

 

[SilverBox]

I'm not sure how how much milling you have done but you seem to be getting a lot of 'steps' in the cut for what is a very softwood.

I understand you freehand cut one side but the steps are on both sides so at least one side it should be reasonably stepless.

This happens when the saw is twisting because it is either being pushed too hard because the chain is not sharp, or the mill is not fitting properly on the top board. This is a limitation of the mini mill so an alaskan will improve this to some extent but it can still happen using an alaskan especially towards the end of the cut in hardwood where the chain is getting blunt.

When cutting narrow boards, any steps can be taken out with a thicknesser but it may not be as easy to do this will a beam.

Thats why I said it just turned out ok, it also pushed over out of perpendicular with the guide board level because the tip was buried in wood for the whole cut. I had to adjust for that on the 2nd cut. The thickness varies from 6.25 to 5.75 depending on where you measure, that is terrible if I was making 1" siding. I need an alaskan, a bigger bar, and a steadier hand to try making finished wood that is thinner. There are alot of step marks. I'm not going to finish the beam, I have a powered hand planer and a flatbed planer, but I'm not going to bother except for top of the beam where the joists will ride on it, I don't really care if the sides or bottom are rough. This is the first thing I've ever tried to mill.

Oh I had to freehand cut both sides, I made both of those cuts from the top with the mini mill, I don't have an alaskan, I have a mini mill and a backhoe, so all cuts are from the top. I wanted to try milling something and see what problems I'd have, I figured I might run into the problems that I am having, ie a mill that only attaches to the saw at 1 point is far inferior to a mill that attaches at 2 points.

 

[Backwoods]

My first attempt at a beam is no where near as straight or smooth as what I have liked but it will work for what I need it for. I used an over sized Alaskan style mill with an over sized bar. My next attempt was milling 42” wide walnut slabs and they turn out much better as the mill and the bar were being fully used giving a much more stable plat form for the mill to run on. The right piece of equipment for the right job makes a difference. The new bar, more practice and straighter logs will have you cutting like a pro in no time.

 

[BobL]

Sorry I reread my response and realized it might have sounded negative. For a first try that was a very good effort. Like Backwoods says - a bit of practice and you should be be fully in business.

 

[SilverBox]

Sorry I reread my response and realized it might have sounded negative. For a first try that was a very good effort. Like Backwoods says - a bit of practice and you should be be fully in business.

no no. I didn't take it as negative, you were right. It could have turned out MUCH better .

 

[SilverBox]

Well I finished up that beam today, the short sides came out much better, but I wasn't able to get my full 14" I wanted. Turned out at 12.5"x6"x16.5'. I need around 1500 psi Fb for that size to work, but I looked over the grain structure and I think I have it.

grain end

grain middle section

grain middle section

continued..

 

[SilverBox]

grain middle

grain end

The finish on the sides is not the best, but the top and bottom that I did today should set up nicely on the posts and carry the joists with no problems.

 

[BIG JAKE]

Nice work Silver box! From what I see the grain looks pretty straight I've seen doug fir grow like a corkscrew and a beam cut from that would be prone to twist more than normal-I think this one will work well for you. I have an 8"x12"x24' beam carrying rafters. Very straight grained without twist. Over 12 years it did twist from one end to the other but not an issue. Deflection is not detectable. Good job and keep us posted doug fir is excellent for staying straight under load.

 

[MotorSeven]

SB, looks like a pretty good job for your first shot! And now the "up-grades" begin........:hmm3grin2orange:

RD